effects of different methods of drying on … · the dairy-based powders are mainly employed for...

1001

EFFECTS OF DIFFERENT METHODS OF DRYING ON ANTIOXIDANT AND MICROSCOPIC CHARACTERISTICS

OF Spirullina platensis ENRICHED SOY YOGURT

Samadrita Sengupta1and Jayati Bhowal

2

Address(es) 1IIEST Shibpur Research Fellow SOCSAT Botanic Garden 711 103 and Howrah West Bengal (+91) 9903780850 2IIEST Shibpur Assistant Professor SOCSAT Botanic Garden 711 103 and Howrah West Bengal (+91) 9831672455

Corresponding author jayatibhowalgmailcom

ABSTRACT

Keywords Spirulina platensis soy yogurt microwave-dried vacuum-dried freeze-dried antioxidant

INTRODUCTION

Dairy products are highly perishable Milk powder has increased shelf life and

stored for long period without substantial loss of quality even at ambient

temperatures (Sharma et al 2012) The dairy-based powders are mainly employed for recombination or reconstitution purposes whereas non-dairy based

powder can be exploited for their distinct functional properties for application as

a food ingredient in several ldquovalue-added foodsrdquo products Like dairy-based powder non- dairy based powdered ingredients are stable produced in large

amount lactose free and convenient for storage Nowadays one of the main areas

of research in food area is the development of functional foods that provide health benefits beyond their basic nutrition Yogurt a fermented food product has

a high worldwide acceptance and considered as ideal matrices to deliver

beneficial nutritional ingredients In addition probiotic bacteria present in yogurt decrease intestinal disorder and chronic diseases Soy bean which is the most

widely grown and utilized legumes in the world has good amino acid profile

contain higher levels of essential fatty acids soluble fiber vitamins minerals

phytochemicals which include isoflavones phytic acid and saponins which have

strong antioxidant properties and have capability of lowering the cholesterol

level Development of new nondairy fermented food products from soybean will provide specific health benefits beyond the conventional dairy products which

have certain limitations from nutritional health aspects Foods prepared from

non-dairy based powdered ingredients like dried soy milk are usually considered to be of lower quality Yogurts both dairy and non-dairy types are highly

nutritious food products for having principally probiotic constituents and

micronutrients that really help to reduce gastro intestinal problems and blood cholesterol level in humanour system and free radicals associated diseases such

as cancer and osteoporosis (Savini et al 2013) The non-dairy yogurts

particularly the soy yogurts are known for such nutritional properties In recent years soy yogurts have been developed with expectedly enhanced nutritional

superiority by incorporating functional lipids such as Gamma linolenic acid

(GLA) Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) and also providing specific antioxidants such as oryzanol and lignans through specific

edible oils (Sengupta et al 2013) Soy yogurts enriched with Spirulina platensis

to provide higher arginine content in protein part and antioxidant such as

selenium zinc tocopherol etc (Morsy et al 2014) Studies showed that viability

of Spirulina platensis incorporated yogurt was higher when compared to control yogurt for both Streptococcus thermophilus and Lactobacillus bulgaricus

throughout the storage period (Priyanka et al 2013) Spirulina platensis is

known to have beneficial influence on the survival of the starter bacterial culture owing to its high protein essential fatty acids such as gamma linolenic acid

vitamins and minerals (Kavimandan and Sharma 2015) It may be pointed out

that soy yogurts having probiotic and other micronutrients can be processed particularly by various drying methodologies to powder with the retention of

various nutrients that in turn can find applications in various kinds of food

products In fact it has been stated by some researchers recently that dried yogurts in

powder form have many applications such as confectionary savory biscuits and

cakes in bakery and in soups dips ready meals baby foods etc (Jaya 2009) In recent days there is great emphasis on adding value to powders and therefore an

inclusive effort from non-dairy plant and powder processors is requisite to

identify the means to add more value Consumers are willing to pay more for soy

milk powders if they can perceive high functionality and quality as well as

multifunctional properties The present investigation aims to convert Spirulina

platensis enriched soy yogurts to powder form by different drying methodologies and evaluate the microstructure and composition of the powders obtained

MATERIAL AND METHODS

All chemicals used were purchased from MERCK India Soybean seeds were

purchased from the local market (New Alipore Market Kolkata West Bengal India) Commercially available milk curd cultures were purchased from

Microbial Type Culture Collection and Gene Bank Chandigarh [Lactobacillus

delbrueckii subsp bulgaricus (MTCC 911) and Streptococcus thermophilus (MTCC 1938)] Spirulina platensis was used as dry biomass having composition

of protein 028 g energy 174 Kcal fat 00 g and carbohydrate 016 g per 500mg

(SUNOVA SPIRULINA Surya Herbal Ltd Noida India)

Spirulina platensis was discussed as an active compound with regard to the combined effects with soy yogurt in dried food formulation

Drying influenced the microscopic and antioxidant properties of soy yogurts and could be used to create new functionalities The

present investigation aimed to convert Spirulina platensis enriched soy yogurts to powder form by different drying methodologies such

as air vacuum freeze and microwave drying and evaluate the microstructure and antioxidant activity of the powders obtained

Antioxidant activities were assayed by using polyphenol assay estimation of carotenoid content DPPH radical scavenging activity and

FRAP assay Structural changes were analyzed using a scanning electron microscope and an X-ray diffraction pattern Freeze-drying

was produced significantly high quality dried Spirulina platensis enriched soy yogurt ie better functional and antioxidant properties

(Polyphenol 0211 Gallic acid equivalent g-1 plt0001 and DPPH activity 1748plusmn011 plt001 of dried yogurt) In addition Spirulina

platensis enriched soy yogurt exhibited an amorphous type molecular structure in all four types of drying methods adopted It could be

concluded that the freeze-drying method could produce superior quality Spirulina platensis enriched dried soy yogurt powder compared

to hot-air-oven and vacuum drying while it is highly comparable to microwave drying

ARTICLE INFO

Received 13 10 2015

Revised 12 8 2016

Accepted 13 11 2016

Published 1 2 2017

Regular article

doi 1015414jmbfs2017641001-1006

J Microbiol Biotech Food Sci Sengupta and Bhowal 2017 6 (4) 1001-1006

1002

Preparation of soy yogurt and Spirulina platensis enriched soy yogurt

The soy milk was made according to the procedure described by Sengupta et al

(2013) The resultant soy milk was then homogenized in a homogenizer (REMI

MOTORS-RQ-122) and pasteurized at 80deg C for 15 min Soy milk was then

cooled down to 40degC for the addition of Spirulina platensis After addition of

Spirulina platensis to pasteurized soy milk (1g of dry biomass of Spirulina platensis 100 ml-1 of soy milk) the mixtures of soy milk and Spirulina platensis

were homogenized again in a homogenizer prior to inoculation with starter

culture until the Spirulina platensis was mixed properly throughout the soy milk Soy milk mixtures were aseptically inoculated with 2 of starter (Lactobacillus

delbrueckii subsp bulgaricus Lactobacillus planterum Lactobacillus casei and Streptococcus thermophilus 1111 vv) The inoculated soy milk containing the

Spirulina platensis was then poured into 100 ml sterile transparent food grade

plastic cups with lids and incubated at 37degC for 24 hours Soy yogurts obtained were stored at 4degC in a refrigerator for further analyses Control soy yogurt was

made by following the above procedure only except incorporation of Spirulina

platensis into soy milk

Drying method of soy yogurt and Spirulina platensis enriched soy yogurt

A quantity of 200g of a fresh Spirulina platensis enriched soy yogurt was dried

separately by using four different drying techniques

Hot- air -oven drying

Spirulina platensis incorporated soy yogurt was dried in hot air oven at 60oC for 24 hours till constant weight was obtained The dried soy yogurt (control) and

Spirulina platensis enriched soy yogurt were sealed airtight and stored at 5degC

until analyses

Vacuum tray drying Spirulina platensis enriched soy yogurt was spread over a petri dish and placed

on the rack of vacuum tray dryer unit (Vacuum Oven 8 dia-12 deep

Temperature up to 150degC Model D- 50 India) Vacuum in the dryer was set at 758 mm Hg and the temperature kept between 45degC to 60degC The drying was

continued for 5 hours until the product became free flowing After cooling the

soy yogurt (control) and Spirulina platensis enriched soy yogurt powder were sealed airtight and stored at 5degC until analyses

Microwave drying

Spirulina platensis enriched soy yogurt was spread over a polymer plate in

Microwave (SAMSUNG MW83HXTL) and heated for 10 minutes at 60degC The product was then collected powdered cooled and was sealed airtight and stored

at 5degC until analyses

Freeze drying

Soy yogurt (control) and Spirulina platensis enriched soy yogurt was frozen in refrigerator at 4oC and then freeze-dried in a freeze dryer (Freezone plus 6

Labconco USA) at -400C and 03 mPa until constant weight (72 hours) The

dried soy yogurt (control) and Spirulina platensis enriched soy yogurt powders were sealed airtight and stored at 5degC until analyses

Handling packaging and grinding of dried soy yogurt (control) and Spirulina

platensis enriched soy yogurt

All the samples sealed in Ziploc bags were placed inside aluminum-coated polyethylene bags To prevent oxidation all the packaged samples were flushed

with nitrogen gas heat sealed and stored at 35degC until further analyses Dried

yogurt powders obtained from different drying processes were ground using

mortar and pestle The hot-air oven dried vacuum dried microwave dried and

freeze dried or lyophilized powder was homogenized by a 12 mesh sized sieve

Physical property of dried soy yogurt (control) and Spirulina platensis

enriched soy yogurt

Water content

The water content of dried soy yogurt (control) and Spirulina platensis enriched

soy yogurt obtained by different drying methods were determined separately

using the standard oven method at 70degC for 24 h (AOAC 1998) The drying cooling and weighing of samples was continued until the difference between two

successive weighing was less than 1 mg

Flow ability evaluation Carrrsquos compressibility index (C) and Hausner ratio

(H)

A quantity of 50g of dried soy yogurt (control) and Spirulina platensis enriched

soy yogurt was filled separately into a graduated glass cylinder and repeatedly

tapped on a shaker The sample was tapped for 500 times and repeated at 3 turns

The volume of powder after tapping and Carrrsquos index percent was measured as equation 1 Hausner ratio is related to inter-particle friction In this test values

less than 125 indicate good flow (asymp 20 Carr) a value greater than 15 indicate

poor flow (asymp 33 Carr)

Carrrsquos compressibility index =Bulked density

Tapped density (1)

Hausner ratio =Tapped density

Bulked density (2)

Antioxidant property of dried soy yogurt (control) and Spirulina platensis

enriched soy yogurt

Polyphenol assay

Estimation of polyphenols was determined using FolinndashCiocalteu reagent

(Singleton and Rossi 1965) with some modification 01 ml dried soy yogurt

(control) and Spirulina platensis enriched soy yogurt (10 mg ml-1 in distilled

water) was extracted separately for 2 h at room temperature on a mechanical shaker To them 1 ml of FolinndashCiocalteu reagent (12 dilution) and 2 ml of 10

Na2CO3 was added The mixture was centrifuged at 20000timesg for 20 min and the

supernatant was decanted and filtered through Whatman No1 filter paper The absorbance of the clear supernatant solution was measured at 765 nm (V-630

UV-VIS Spectrophotometer JASCO) Gallic acid was used as a standard Each

sample was analyzed twice with duplicates Results were expressed as mg GAE 100 g-1 dry weight

1 1-diphenyl-2-picrylhydrazyl (DPPH) assay

DPPH radical scavenging activity was determined using 1 1-diphenyl-2-

picrylhydrazyl (DPPH) assay (Bansal et al 2014) with some modification 05 ml dried soy yogurt (control) and Spirulina platensis enriched soy yogurt (10 mg

ml-1 in distilled water) was added separately to 25 ml DPPH reagent (02 mM)

The reaction mixture was kept in dark at ambient temperature for 30 min The absorbance was measured using a spectrophotometer at 517 nm (V-630 UV-VIS

Spectrophotometer JASCO) DPPH radical scavenging activity () was

calculated using following formula

Inhibition =(Absorbance 517 control ndash Absorbance 517 extract)

(Absorbance 517 control)times 100 (3)

Ferric reducing antioxidant power (FRAP) assay

Reducing power was determined using ferric reducing antioxidant power (FRAP) assay (Barahona et al 2011) with some modification 05 ml dried soy yogurt


water) was added separately to 25 ml FRAP reagent The FRAP reagent consist of 300 mM acetate buffer (31 g sodium acetate + 16 ml glacial acetic acid made

up to 1 L with distilled water pH = 36) 10 mM TPTZ in 40 mM HCl and 20

mM FeCl36H2O in the ratio of 1011 The reaction mixture was kept in dark at ambient temperature for 10 min The absorbance was measured using a

spectrophotometer at 593 nm (V-630 UV-VIS Spectrophotometer JASCO)

Reducing power was calculated using following formula

119877119890119889119906119888119894119899119892 119901119900119908119890119903 = 119860119887119904593 119904119886119898119901119897119890 minus 119860119887119904 593 119865119877119860119875 119903119890119886119892119890119899119905 (4)

Carotenoid estimation

05 ml dried soy yogurt (control) and Spirulina platensis enriched soy yogurt (10

mg ml-1 in distilled water) was centrifuged separately at 3000 rpm for 5 minutes The pellet was washed with distilled water 2-3 times To the pellet 2-3 ml of

acetone (85) was added which was then subjected to repeated freezing and

thawing The suspension was centrifuged and the supernatant containing pigment was collected The extraction was repeated till the supernatant became colorless

for complete recovery of carotenoid The pooled fractions of supernatants were

made-up to a final known volume The absorbance was taken at 450nm using 85 acetone as blank and the total amount of carotenoids was calculated in mg g-

1 as follows (Saleh et al 2011)

119862 =119863 times 119881119865

2500 times 100 (5)


1003

D=OD at 450nm V = Volume of the extract F = Dilution factor (Assuming that average extinction coefficient is 2500)

Color parameter of dried soy yogurt (control) and Spirulina platensis

enriched soy yogurt

Color parameters were determined using colorimeter (Minolta Chroma meter CR-300 USA) Dried soy yogurt (control) and Spirulina platensis enriched soy

yogurt were poured into a clear glass petri dish and color coordinate values

(lightness L redness a and yellowness b) were recorded separately

X-Ray Diffraction pattern of dried soy yogurt (control) and Spirulina


X-ray diffraction patterns of dried soy yogurt (control) and Spirulina platensis enriched soy yogurt were obtained at room temperature using a Rigaku Multiflex

powder diffractometer (CuKα radiation generator) operated at a voltage of 40 kV

Powdered dried yogurt samples were analyzed separately at two theta (2θ) angle range of 10ndash30

Morphology analysis of dried soy yogurt (control) and spirulina platensis

enriched soy yogurt using scanning electron microscopic analysis (SEM)

Dried soy yogurt (control) and Spirulina platensis enriched soy yogurt at micro

level were examined separately by scanning electron microscope for desired

structural properties The dried Soy yogurt and Spirulina platensis incorporated

soy yogurt was previously fixed on an iron stub and then made electrically conductive by coating in a vacuum chamber with a thin layer of gold for 40 s

The pictures were taken at an excitation voltage of 15 kv at different

magnifications varying from 1500-1600

Statistical analysis

Statistical analysis was performed by using analysis of variance (ANOVA) and

the means were compared across groups by Tukey test All analyses were carried

out in triplicates repeated at least twice with the Origin Pro 8 and the significant

differences were determined at p le 005

RESULTS AND DISCUSSION

Soy yogurt is generally dried by freeze spray microwave and vacuum drying Fazaeli et al (2012) observed that among the different drying methods freeze-

drying is one of the most advanced methods for drying food products since it retains taste aroma flavor color and the nutritional quality In addition (Rybka

and Kailasapathy 1997) also observed that freeze-dried soy yogurt is the

authentic product in comparison to yogurt obtained using other conventional drying methods Another study revealed that there is no significant change on the

final contents of total protein casein serum and non-protein nitrogen obtained

from freeze-drying at -40 Radaeva et al (1975) found that survival of lactic

acid bacteria in yogurt was 50-60 during freeze-drying at -40 Kitawaki et

al (2009) showed that freeze-dried soy yogurt is beneficial in preventing hepatic

lipid accumulation in rats From the above literature it was revealed that that freeze drying best choice of the drying methods tested for evaluation of the soy

yogurt Other drying techniques also work well but should not be used for soy

yogurts due to sensitivity to oxidation


enriched soy yogurt

The physical properties of yogurt powder are shown in Tab 1 No significant

differences were observed in water content between Product-I and Product-V Data showed that vacuum dried yogurt sample had the significantly highest

(367plusmn067 plt001) and the microwave dried had the significantly lowest

moisture content (189plusmn055 plt0001) in comparison with Product-I Hot air and freeze dried yogurt samples had moisture close to each other During vacuum

drying the yogurt sample was expanded under the vacuum

Table 1 Selected physical properties of dried soy yogurt (control) and Spirulina platensis enriched soy yogurt

Materials Water content () Bulk density (g cm-3) Tapped density (g cm-3) C HR

Product-I (control) 255plusmn061 022plusmn008 041plusmn049 5365plusmn021 186plusmn048

Product-II 262plusmn056 039plusmn004a 059plusmn004a 6610plusmn005a 151plusmn032a

Product-III 367plusmn067b 032plusmn004a 058plusmn003b 5517plusmn006a 181plusmn011b

Product-IV 189plusmn055c 029plusmn007 044plusmn009b 6590plusmn003a 151plusmn023b

Product-V 252plusmn098 038plusmn002a 047plusmn011a 6666plusmn003a 123plusmn016c

The data are mean plusmn SD and significantly different at aP lt 005 bP lt 001 and cPlt 0001 vs Product-I SP- Spirulina platensis C- Carrrsquos Index HR- Hausner ratio SP- Spirulina platensis Product-I soy yogurt (freeze dried) Product-II SP soy yogurt (hot air oven

dried)Product-III SP soy yogurt (vacuum dried) Product-IV SP soy yogurt (microwave dried) Product-V SP soy yogurt freeze dried

Compressibility is the ability to reduce volume by tapping developed by Carr

(1965) as an average and indirect measure of cohesion forces The flowability

scale is ldquouniversalrdquo as it has been constructed on previous measurements of 300 different powders from [0ndash19] very poor [20ndash39] poor [40ndash59] not good [60ndash

69] normal [70ndash79] good [80ndash89] fairly good and [90ndash100] very good All the

yogurt powders that we had dried had been under the value of 60 except Product-I and Product-III corresponding to ldquonormal flowabilityrdquo Compressibility

for the product was followed the same tendency as the Hausner ratio declining

when vacuum dried applied Note that a Product-II IV and V presented a normal flow without special problems with a flowability index value of above 60 Only

the Product-III presented significantly worse flowability (5517plusmn006 plt005)

than Product-I Product-I could not present good flowability because of its low content of carbohydrate and protein percentage Product-IV presented extreme

values for low Hausner ratio (123plusmn016 plt0001) together with the best

flowability index (666plusmn003 plt005) This product should therefore present high

internal homogeneity due to Spirulina platensis incorporation and quite

ldquoexceptional propertiesrdquo within the drying techniques studied This flowability index value is quite unusual for non-dairy powder


enriched soy yogurt

Antioxidant property of dried soy yogurt (control) and Spirulina platensis enriched soy yogurt affected by different drying methods is illustrated in Fig 1

Spirulina are believed to be a rich source of polyphenol antioxidants Spirulina

platensis fortification was found to bring about a significant increase in the

antioxidant capacity but drying was found to bring about a reduction Total poly phenolic content was significantly the highest in product-IV (0185 GAE g-1

plt005) and Product-V (0211 GAE g-1 plt005 of dried yogurt) Product-V

showed significantly highest total phenolic content (0211 GAE g-1 plt0001 of dried yogurt) in comparison with Product-II and Product-III However not a big

difference in percentage increase of activity was observed for all four drying

treatment with Spirulina platensis fortification In the FRAP assay the antioxidant activity of Product-II and Product-III was not affected by respective

drying treatments On the contrary in the DPPH assay the antioxidant activity

was significantly influenced for Product-II (1458plusmn004 plt005 of dried yogurt) and Product-III (1426plusmn002 plt005 of dried yogurt) DPPH radical

scavenging activities were not significantly different between Product-IV

(1567plusmn001 plt001 of dried yogurt) and Product-V (1748plusmn011 plt001 of

dried yogurt) while both were significantly higher than Product-II and Product-

III The results showed (Fig 1) that the total carotenoid content of powders obtained by Spirulina platensis incorporated soy yogurt was significantly

influenced by different drying method The highest carotenoid content (577 mg g-

1 of dried yogurt) was for Product-III whilst the Product-II that was hot air dried had the lowest carotenoid content (327 mg g-1 of dried yogurt)


1004

Product- I Product-II Product-III Product-IV Product-V

000

005

010

015

020

025

Poly

phen

ol C

onte

nt m

g G

AE g a

a

a

a


0

2

4

6

8

10

12

14

16

18

20

22

DPP

H R

adic

al S

cave

ngin

g Ac

tivity

()

a a

b

b


000

005

010

015

020

025

030

035

040

FRAP

Abso

rben

ce a

t 593

nm

b

a

a

a


0

1

2

3

4

5

6

Tota

l Car

oten

oid

Con

tent

(mg

g)

a

a

b

a

Fig 1 Polyphenol content DPPH radical scavenging activity FRAP and carotenoid content of dried soy yogurt (control) and Spirulina platensis enriched soy yogurtSP- Spirulina platensis C- Carrrsquos Index HR- Hausner ratio SP- Spirulina platensis Product-I soy yogurt (freeze dried) Product-I soy

yogurt (freeze dried) Product-II SP soy yogurt (hot air oven dried)Product-III SP soy yogurt (vacuum dried) Product-IV SP soy yogurt (microwave dried) Product-

V SP soy yogurt freeze dried GAE Gallic acid equivalent DPPH 1 1-diphenyl-2-picrylhydrazyl FRAP Ferric reducing antioxidant power

There was no significant difference between Product-IV and Product-V in terms

of total carotenoid content It is evident that vacuum drying was more effective in the retention of total carotenoid than air-drying Therefore it can be concluded

that the main reason for carotenoid degradation is due to loss of anthocyanin It is

clear that the freeze-drying process can substantially preserve the nutritional value of Spirulina platensis in terms of total antioxidant activity From the results

of the various tests in the study the quality of freeze-dried Spirulina platensis

incorporated soy yogurt powder products is seen to be highest followed by microwave-dried powder vacuum-dried powder air-dried powder and then

powders from soy yogurt as control


enriched soy yogurt

It was observed from Tab 2 that the Lightness (L) redness (a) yellowness (b)

and hue angle (h) were significantly different among the dried Spirulina platensis

enriched soy yogurt The highest L value (5934plusmn265 plt001) and lowest a

value (-1748plusmn098 plt001) was observed in Product-V in comparison with

Product-II III and IV The highest L value could attribute to minimal color deterioration Freeze-drying can retarded oxidation and other chemical reactions

and thus minimal color deterioration (Ratti et al 2001) Meanwhile the lowest

L value (4057plusmn467 plt005) and highest a value (-1458plusmn558 plt005) was observed in Product-II The lowest L value could attribute to color degradation

Oven drying can cause oxidative degradation and thus lead to color change (turn

into darker color) No significant difference was observed in b value (yellowness) between Product-IV and Product-V while there was a highly

significant difference between Product-II and Product-III (Tab 2) Product-IV

obtained a higher h value (15077plusmn764 plt005) compared to Product-II II and V suggesting that microwave dried Product-IV is more vivid in its dark green

color implying that it will be more attractive and appealing to consumers The

overall distinct vivid dark green color of the Product-IV may be indicative of high chlorophyll retention The minimal color change of product produced by

microwave dried Product-IV and freeze-dried Product-V suggests the

appropriateness of these processes to produce high quality products

Table 2 Color measurements of soy yogurt and Spirulina platensis incorporated soy yogurt powder obtained by different drying methods

Materials L a b h

Product- I (control) 7564plusmn627 026plusmn285 1225plusmn087 8385plusmn925

Product-II 4057plusmn467a -1458plusmn558a 681plusmn054a 13011plusmn831c

Product-III 5174plusmn625c -1426plusmn354a 635plusmn034c 14379plusmn846b

Product-IV 4627plusmn384a -1567plusmn126c 765plusmn087b 15077plusmn764a

Product-V 5934plusmn265b -1748plusmn098b 729plusmn069b 14407plusmn647b

The data are mean plusmn SD and significantly different at aP lt 005 bP lt 001 and cPlt 0001 vs Product-I SP- Spirulina platensis C- Carrrsquos

Index HR- Hausner ratio SP- Spirulina platensis Product-I soy yogurt (freeze dried) Product-II SP soy yogurt (hot air oven


X-ray diffraction patterns of dried soy yogurt (control) and Spirulina


The X-ray diffraction patterns of the soy yogurt (control) and Spirulina platensis

enriched soy yogurt gave valuable information about structural aspects of the Spirulina platensis (Fig 2) In this study Product-II III IV and V had a

significant influence on the degree of dispersion and aggregation in soy yogurt

XRD is a very common technique used to confirm the crystalline-amorphous state of dried yogurt powder Dried yogurt obtained from all the form of drying

methods exhibited amorphous nature Amorphous products produce a broad

background pattern while crystalline material exhibits sharp peaks while Crystalline nature obtained from XRD is expected due to presence of raffinose

and stachyose sugar Rapid drying of low molecular weight sugar present in

yogurt tends to produce amorphous metastable state of dried products due to

insufficient time to crystallize Drying methods of yogurt showed no crystalline

peaks formation In case of freeze drying the temperature of yogurt was less than 50degC Crystal formation generally occurs above 50degC Thus in case of freeze-

drying less crystalline is preferred These figures exhibit essentially similar

diffraction patterns (2θ values) for all samples suggesting that dried yogurts did not undergo any structural modifications (Fig 2) However a major reduction in

relative intensities of their peaks particularly for Product-II and Product-IV might

be due to reduction in crystallinity and presence of amorphous state in the samples Therefore it was expected that in the case of drying by freeze drier

Spirulina platensis incorporated dried soy yogurt particles with less crystallinity

were produced However it was interesting to note that the intensity count for Product-II as shown in the diffractograms was significantly lower compared to

the other three powder products


1005

10 20 30600

800

1000

1200

1400 10 20 30

1000

1500

2000

2500 10 20 30

800

1000

1200

1400

1600

1800

200010 20 30

1000

1500

2000

2500 10 20 30600

800

1000

1200

1400

10 20 30

Angle two theta

Product-II

Product-III

intens

ity(ar

b unit

s)

A

Product-IV

Product-V

Product-I

Fig 2 X-ray diffraction patterns of dried soy yogurt (control) and Spirulina platensis enriched soy yogurt

SP- Spirulina platensis C- Carrrsquos Index HR- Hausner ratio SP- Spirulina platensis Product-I soy yogurt (freeze dried) Product-II SP soy yogurt (hot air oven dried) Product-III SP soy yogurt (vacuum dried) Product-IV SP soy yogurt (microwave dried) Product-V SP soy yogurt freeze dried

Product-I Product-II

Product-III Product-IV

Product-V

Fig 3 Scanning electron micrographs (SEM) of soy yogurt and Spirulina platensis enriched soy yogurt (magnification of 800times20 kV)

SP- Spirulina platensis Product-I soy yogurt (freeze dried) Product-II SP soy

yogurt (hot air oven dried)Product-III SP soy yogurt (vacuum dried) Product-IV SP soy yogurt (microwave dried) Product-V SP soy yogurt freeze

driedProduct- I soy yogurt-freeze dried Product-II SP soy yogurt hot air oven

Dried Product-III SP soy yogurt vacuum dried Product-IV SP soy yogurt microwave dried Product-V SP soy yogurt freeze dried

Scanning electron micrographs (SEM) of dried soy yogurt (control) and

Spirulina platensis enriched soy yogurt

Scanning electron micrographic studies of soy yogurt and Spirulina platensis enriched soy yogurt are shown in Fig 3 The microstructure of Product-II was

compact and exhibited irregular particles with sharp edges and considerable

indentation because of crushing into powder The microstructure of Product-III and Product-IV was smooth and flaky with uniform thickness Product-V

showed a skeletal like structure and was more porous than the other Product This

is due to the ice in the material during freeze drying helps prevent shrinkage and collapse of the structure and shape resulting in an insignificant change in volume

CONCLUSION

The primary objective of manufacturing dried yogurt in powder form is to

increase the shelf life of yogurt Freeze-drying is a physical phenomenon of sublimation which consists of first freezing the yogurt and then reducing the

surrounding presence to allow the frozen yogurt to sublimate directly for solid

phase to gaseous phase without passing through the liquid state Freeze dried products have very good capacity to take up water again since have extremely

large internal surface area and they Thus freeze-dried products can be stored

from very long time without too much loss of nutritional quality Thus in freeze drying products ingredients are preserved with good nutritional value Moreover

freely dried yogurt retained flavor color taste in comparison to yogurt obtained

using other drying methods (Fazaeli et al 2012) and also has better rehydration property Absence of air causes very less deterioration of food product Another

study revealed that freeze-drying did not affect the final content of protein casein

serum and non-protein nitrogen Again it was observed that in yogurt 50- 60 of lactic acid bacteria were survived during freeze-drying (Radaeva 1975) That is

why freeze-drying method is best drying methods Drying techniques were

shown to exert significant effect on Spirulina platensis enriched dried soy yogurt Freeze-drying was most suitable method to produce high quality dried Spirulina

platensis enriched soy yogurt ie better functional and antioxidant properties

Overall our study concludes that the freeze drying method can produce superior quality Spirulina platensis enriched dried soy yogurt powder compared to hot-air-

oven and vacuum drying while it is highly comparable to microwave drying The

study provides an opportunity to the powder processing industry in selecting a


1006

better drying technique that can be utilized for the production of high quality yogurt powder a complementary formulated as a tablet from soy yogurt powder

is possible and also may be therapeutically effective against lactose-intolerance

syndrome and preventing antibiotic-associated diarrhea

REFERENCES

AOAC 1998 Official Methods of Analysis Association of Official Analytical

Chemists Washington DC USA

Bansal V Sharma H K amp Nanda V (2014) Optimisation of spray drying

process parameters for low‐fat honey‐based milk powder with antioxidant

activity Int J Food Sci Technol 49 (4) 1196-1202

httpdxdoiorg101111ijfs12416

Barahona T Chandiacutea NP Encinas MV Matsuhiro B amp Zuacutentildeiga EA (2011) Antioxidant capacity of sulfated polysaccharides from seaweeds A

kinetic approach Food Hydrocoll 25 529-535

httpdxdoiorg101016jfoodhyd201008004 Carr RL (1965) Evaluating flow properties of solids Chem Eng J 72 163ndash

168

Fazaeli M Tahmasebi M amp EmamDjomeh Z (2012) Characterization of food texture application of Microscopic technology Current Microscopy

Contributions to Advances in Science and Technology1 855-871

Kavimandan A amp Sharma S (2015) Role of Spirulina platensis as an enhancer

of probiotic organisms in whey International journal of dairy science research

3(1) 1-6

Kitawaki R Nishimura YY Takagi N Iwasaki M Tsuzuki K amp Fukuda M (2009) Effects of Lactobacillus Fermented Soymilk and Soy Yogurt on

Hepatic Lipid Accumulation in Rats Fed a Cholesterol-Free Diet Biosci

Biotechnol Biochem 73 (7) 1484ndash1488 httpdxdoiorg101271bbb80753 Malik P Kempanna C Narasimha M amp Anjum (2013) Quality

Characteristics of Yoghurt Enriched with Spirulina Powder Mysore J Agric

Sci 47 (2) 354-359 Morsy OM Sharoba AM EL-Desouky AI Bahlol HEM amp Abd El

Mawla EM Production and evaluation of some extruded food products using

spirulina algae Annals of Agric Sci 52(4) 2014 Jaya S (2009) Microstructure Analysis of Dried Yogurt Effect of Different

Drying Methods Int J Food Prop 12 469ndash481

httpdxdoiorg10108010942910701772071 Ratti C (2001) Hot air and freeze-drying of high-value foods ndash a review J

Food Eng 49 311ndash319 httpdxdoiorg101016S0260-8774(00)00228-4

Saleh AM Dhar DW and Singh PK (2011) Comparative pigment profiles of different Spirulina strains R in Biotech 2(2) 67-74

Savini I Catani M V Evangelista D Gasperi V amp Avigliano L (2013)

Obesity-Associated Oxidative Stress Strategies Finalized to Improve Redox

State Int J Mol Sci 14(5) 10497ndash10538

httpdxdoiorg103390ijms140510497

Sengupta S Bhowal J Bhattacharyya DK (2013) Development of new kinds of Soy yogurt containing functional lipids as superior quality food Annals of

Biological Research 4144-151

Sharma A Jana AH amp Chavan R S(2012) Functionality of Milk Powders

and Milk‐Based Powders for End Use ApplicationsmdashA Review Comp Rev Food Sci Food 11 518-528 httpdxdoiorg101111j1541-4337201200199x

Radaeva IA Shulrsquokina SP Kocherga SI amp Efron BG (1975) Effect of

freezing regimes in freeze-drying on yogurt quality Molochnaya Promyshlennost 5 22-23

Rybka S amp Kailasapathy K(1997) Effect of freeze drying and storage on the

microbiological and physical properties of AB yogurtrdquo Milchwissenschaft 52 390-394

Singleton VL amp Rossi J A (1965) Colorimetry of total phenolics with

phosphomolybdic-phosphotungtic acid reagent Am J Enol Vitic 144-158 16

144-158


1002

Preparation of soy yogurt and Spirulina platensis enriched soy yogurt

The soy milk was made according to the procedure described by Sengupta et al

(2013) The resultant soy milk was then homogenized in a homogenizer (REMI

MOTORS-RQ-122) and pasteurized at 80deg C for 15 min Soy milk was then

cooled down to 40degC for the addition of Spirulina platensis After addition of

Spirulina platensis to pasteurized soy milk (1g of dry biomass of Spirulina platensis 100 ml-1 of soy milk) the mixtures of soy milk and Spirulina platensis

were homogenized again in a homogenizer prior to inoculation with starter

culture until the Spirulina platensis was mixed properly throughout the soy milk Soy milk mixtures were aseptically inoculated with 2 of starter (Lactobacillus

delbrueckii subsp bulgaricus Lactobacillus planterum Lactobacillus casei and Streptococcus thermophilus 1111 vv) The inoculated soy milk containing the

Spirulina platensis was then poured into 100 ml sterile transparent food grade

plastic cups with lids and incubated at 37degC for 24 hours Soy yogurts obtained were stored at 4degC in a refrigerator for further analyses Control soy yogurt was

made by following the above procedure only except incorporation of Spirulina

platensis into soy milk

Drying method of soy yogurt and Spirulina platensis enriched soy yogurt

A quantity of 200g of a fresh Spirulina platensis enriched soy yogurt was dried

separately by using four different drying techniques

Hot- air -oven drying

Spirulina platensis incorporated soy yogurt was dried in hot air oven at 60oC for 24 hours till constant weight was obtained The dried soy yogurt (control) and

Spirulina platensis enriched soy yogurt were sealed airtight and stored at 5degC

until analyses

Vacuum tray drying Spirulina platensis enriched soy yogurt was spread over a petri dish and placed

on the rack of vacuum tray dryer unit (Vacuum Oven 8 dia-12 deep

Temperature up to 150degC Model D- 50 India) Vacuum in the dryer was set at 758 mm Hg and the temperature kept between 45degC to 60degC The drying was

continued for 5 hours until the product became free flowing After cooling the

soy yogurt (control) and Spirulina platensis enriched soy yogurt powder were sealed airtight and stored at 5degC until analyses

Microwave drying

Spirulina platensis enriched soy yogurt was spread over a polymer plate in

Microwave (SAMSUNG MW83HXTL) and heated for 10 minutes at 60degC The product was then collected powdered cooled and was sealed airtight and stored

at 5degC until analyses

Freeze drying

Soy yogurt (control) and Spirulina platensis enriched soy yogurt was frozen in refrigerator at 4oC and then freeze-dried in a freeze dryer (Freezone plus 6

Labconco USA) at -400C and 03 mPa until constant weight (72 hours) The

dried soy yogurt (control) and Spirulina platensis enriched soy yogurt powders were sealed airtight and stored at 5degC until analyses

Handling packaging and grinding of dried soy yogurt (control) and Spirulina


All the samples sealed in Ziploc bags were placed inside aluminum-coated polyethylene bags To prevent oxidation all the packaged samples were flushed

with nitrogen gas heat sealed and stored at 35degC until further analyses Dried

yogurt powders obtained from different drying processes were ground using

mortar and pestle The hot-air oven dried vacuum dried microwave dried and

freeze dried or lyophilized powder was homogenized by a 12 mesh sized sieve


enriched soy yogurt

Water content

The water content of dried soy yogurt (control) and Spirulina platensis enriched

soy yogurt obtained by different drying methods were determined separately

using the standard oven method at 70degC for 24 h (AOAC 1998) The drying cooling and weighing of samples was continued until the difference between two

successive weighing was less than 1 mg

Flow ability evaluation Carrrsquos compressibility index (C) and Hausner ratio

(H)

A quantity of 50g of dried soy yogurt (control) and Spirulina platensis enriched

soy yogurt was filled separately into a graduated glass cylinder and repeatedly

tapped on a shaker The sample was tapped for 500 times and repeated at 3 turns

The volume of powder after tapping and Carrrsquos index percent was measured as equation 1 Hausner ratio is related to inter-particle friction In this test values

less than 125 indicate good flow (asymp 20 Carr) a value greater than 15 indicate

poor flow (asymp 33 Carr)

Carrrsquos compressibility index =Bulked density

Tapped density (1)

Hausner ratio =Tapped density

Bulked density (2)


enriched soy yogurt

Polyphenol assay

Estimation of polyphenols was determined using FolinndashCiocalteu reagent

(Singleton and Rossi 1965) with some modification 01 ml dried soy yogurt


water) was extracted separately for 2 h at room temperature on a mechanical shaker To them 1 ml of FolinndashCiocalteu reagent (12 dilution) and 2 ml of 10

Na2CO3 was added The mixture was centrifuged at 20000timesg for 20 min and the

supernatant was decanted and filtered through Whatman No1 filter paper The absorbance of the clear supernatant solution was measured at 765 nm (V-630

UV-VIS Spectrophotometer JASCO) Gallic acid was used as a standard Each

sample was analyzed twice with duplicates Results were expressed as mg GAE 100 g-1 dry weight

1 1-diphenyl-2-picrylhydrazyl (DPPH) assay

DPPH radical scavenging activity was determined using 1 1-diphenyl-2-

picrylhydrazyl (DPPH) assay (Bansal et al 2014) with some modification 05 ml dried soy yogurt (control) and Spirulina platensis enriched soy yogurt (10 mg

ml-1 in distilled water) was added separately to 25 ml DPPH reagent (02 mM)

The reaction mixture was kept in dark at ambient temperature for 30 min The absorbance was measured using a spectrophotometer at 517 nm (V-630 UV-VIS

Spectrophotometer JASCO) DPPH radical scavenging activity () was

calculated using following formula

Inhibition =(Absorbance 517 control ndash Absorbance 517 extract)

(Absorbance 517 control)times 100 (3)

Ferric reducing antioxidant power (FRAP) assay

Reducing power was determined using ferric reducing antioxidant power (FRAP) assay (Barahona et al 2011) with some modification 05 ml dried soy yogurt


water) was added separately to 25 ml FRAP reagent The FRAP reagent consist of 300 mM acetate buffer (31 g sodium acetate + 16 ml glacial acetic acid made

up to 1 L with distilled water pH = 36) 10 mM TPTZ in 40 mM HCl and 20

mM FeCl36H2O in the ratio of 1011 The reaction mixture was kept in dark at ambient temperature for 10 min The absorbance was measured using a

spectrophotometer at 593 nm (V-630 UV-VIS Spectrophotometer JASCO)

Reducing power was calculated using following formula

119877119890119889119906119888119894119899119892 119901119900119908119890119903 = 119860119887119904593 119904119886119898119901119897119890 minus 119860119887119904 593 119865119877119860119875 119903119890119886119892119890119899119905 (4)

Carotenoid estimation

05 ml dried soy yogurt (control) and Spirulina platensis enriched soy yogurt (10

mg ml-1 in distilled water) was centrifuged separately at 3000 rpm for 5 minutes The pellet was washed with distilled water 2-3 times To the pellet 2-3 ml of

acetone (85) was added which was then subjected to repeated freezing and

thawing The suspension was centrifuged and the supernatant containing pigment was collected The extraction was repeated till the supernatant became colorless

for complete recovery of carotenoid The pooled fractions of supernatants were

made-up to a final known volume The absorbance was taken at 450nm using 85 acetone as blank and the total amount of carotenoids was calculated in mg g-

1 as follows (Saleh et al 2011)

119862 =119863 times 119881119865

2500 times 100 (5)


1003



enriched soy yogurt



































enriched soy yogurt





























enriched soy yogurt


















1004


000

005

010

015

020

025

Poly

phen

ol C

onte

nt m

g G

AE g a

a

a

a


0

2

4

6

8

10

12

14

16

18

20

22

DPP

H R

adic

al S

cave

ngin

g Ac

tivity

()

a a

b

b


000

005

010

015

020

025

030

035

040

FRAP

Abso

rben

ce a

t 593

nm

b

a

a

a


0

1

2

3

4

5

6

Tota

l Car

oten

oid

Con

tent

(mg

g)

a

a

b

a












enriched soy yogurt

















Materials L a b h





























1005

10 20 30600

800

1000

1200

1400 10 20 30

1000

1500

2000

2500 10 20 30

800

1000

1200

1400

1600

1800

200010 20 30

1000

1500

2000

2500 10 20 30600

800

1000

1200

1400

10 20 30

Angle two theta

Product-II

Product-III

intens

ity(ar

b unit

s)

A

Product-IV

Product-V

Product-I





Product-V













CONCLUSION


















1006




REFERENCES










168





3(1) 1-6


























144-158


1003



enriched soy yogurt



































enriched soy yogurt





























enriched soy yogurt


















1004


000

005

010

015

020

025

Poly

phen

ol C

onte

nt m

g G

AE g a

a

a

a


0

2

4

6

8

10

12

14

16

18

20

22

DPP

H R

adic

al S

cave

ngin

g Ac

tivity

()

a a

b

b


000

005

010

015

020

025

030

035

040

FRAP

Abso

rben

ce a

t 593

nm

b

a

a

a


0

1

2

3

4

5

6

Tota

l Car

oten

oid

Con

tent

(mg

g)

a

a

b

a












enriched soy yogurt

















Materials L a b h





























1005

10 20 30600

800

1000

1200

1400 10 20 30

1000

1500

2000

2500 10 20 30

800

1000

1200

1400

1600

1800

200010 20 30

1000

1500

2000

2500 10 20 30600

800

1000

1200

1400

10 20 30

Angle two theta

Product-II

Product-III

intens

ity(ar

b unit

s)

A

Product-IV

Product-V

Product-I





Product-V













CONCLUSION


















1006




REFERENCES










168





3(1) 1-6


























144-158


1004


000

005

010

015

020

025

Poly

phen

ol C

onte

nt m

g G

AE g a

a

a

a


0

2

4

6

8

10

12

14

16

18

20

22

DPP

H R

adic

al S

cave

ngin

g Ac

tivity

()

a a

b

b


000

005

010

015

020

025

030

035

040

FRAP

Abso

rben

ce a

t 593

nm

b

a

a

a


0

1

2

3

4

5

6

Tota

l Car

oten

oid

Con

tent

(mg

g)

a

a

b

a












enriched soy yogurt

















Materials L a b h





























1005

10 20 30600

800

1000

1200

1400 10 20 30

1000

1500

2000

2500 10 20 30

800

1000

1200

1400

1600

1800

200010 20 30

1000

1500

2000

2500 10 20 30600

800

1000

1200

1400

10 20 30

Angle two theta

Product-II

Product-III

intens

ity(ar

b unit

s)

A

Product-IV

Product-V

Product-I





Product-V













CONCLUSION


















1006




REFERENCES










168





3(1) 1-6


























144-158


1005

10 20 30600

800

1000

1200

1400 10 20 30

1000

1500

2000

2500 10 20 30

800

1000

1200

1400

1600

1800

200010 20 30

1000

1500

2000

2500 10 20 30600

800

1000

1200

1400

10 20 30

Angle two theta

Product-II

Product-III

intens

ity(ar

b unit

s)

A

Product-IV

Product-V

Product-I





Product-V













CONCLUSION


















1006




REFERENCES










168





3(1) 1-6


























144-158


1006




REFERENCES










168





3(1) 1-6


























144-158

effects of different methods of drying on … · the dairy-based powders are mainly employed for...

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